<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        a:link{
            color: red;
        }
        a:visited{
            color: green;
        }
        a:hover{
            color: blue;
        }
        a:active{
            color: yellow;
        }

        ul li:first-child{
            color: red;
        }

        ul li:last-child{
            color: blue;
        }
        ul li:nth-child(2){
            color: green;
        }
        ul li:nth-child(odd){
            color: green;
        }
        ul li:nth-child(even){
            color: red;
        }
    </style>
</head>
<body>
    <a href="https://www.baidu.com">hello world</a>

    <ul>
        <li>hello world</li>
        <li>hello world</li>
        <li>hello world</li>
        <li>hello world</li>
        <li>hello world</li>
    </ul>
    
</body>
</html>